Method for manufacturing coated body and apparatus for manufacturing coated body

Abstract

[Problem] To manufacture a coated body with good properties. [Solution] (a) Step: Apply a first coating liquid to the first surface of the substrate 1 taken out from the transfer section to form a first coating liquid layer 3a; (b) Step: After step (a), apply a second coating liquid to the first coating liquid layer to form a second coating liquid layer 4a; (c) Step: After step (b), dry the first coating liquid layer and the second coating liquid layer to form a coating film 3b and a coating film 4b; (d) Step: Place the substrate with the coating film 3b and the coating film 4b formed thereon into the transfer section to manufacture a coated body 5. Moreover, step (a) involves applying the first coating liquid to the first surface of the substrate, and step (b) involves spraying the second coating liquid onto the first surface of the substrate.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for manufacturing a coated body, and particularly to a method and apparatus for manufacturing a coated body for use in battery separators and the like. [Previous Technology]

[0002] In recent years, batteries such as lithium-ion batteries have been widely used in automobiles and infrastructure. In batteries such as lithium-ion batteries, the positive electrode material and the negative electrode material are separated by a porous membrane called a separator. The separator has, for example, a plurality of micropores through which lithium ions can pass, and the lithium ions move between the positive electrode material and the negative electrode material through these pores, thereby repeatedly charging and discharging. As described above, the separator separates the positive electrode material and the negative electrode material, and has the function of preventing short circuits.

[0003] In addition, when the inside of the battery becomes hot for some reason, the micropores of the separator close, thereby stopping the movement of lithium ions and stopping the battery's function (shutdown function).

[0004] As described above, the separator is responsible for the safety device of the battery, making it important to improve the mechanical strength or heat resistance of the separator.

[0005] For example, Patent Document 1 (Japanese Patent Application Publication No. 2016-183209) discloses a technique in which a coating layer containing inorganic particles and an adhesive resin composition is formed on at least one side of a polyolefin resin porous membrane.

[0006] Furthermore, Patent Document 2 (Japanese Patent Application Publication No. 2019-72666) discloses a coating apparatus for suppressing the mixing of a plurality of coating liquids, and it comprises: a first mold, which applies the first coating liquid onto a sheet to form a first layer while discharging the first coating liquid from a first outlet and contacting a support roller; and a second mold, which applies the second coating liquid onto the first layer on the sheet to form a second layer while discharging the second coating liquid from a second outlet and contacting a support roller.

[0007] [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 2016-183209 [Patent Document 2] Japanese Patent Application Publication No. 2019-72666 [Summary of the Invention]

[0008] [Problem to be solved by the invention] In order to improve the properties of coatings such as battery separators, the inventors of this case have researched and developed coating technology for forming coatings on the surface of a substrate.

[0009] During this research and development process, when the coating layer is made into multiple layers, there is a problem of coating liquid mixing. In order to solve this problem, we conducted in-depth research and developed a good coating technology.

[0010] Other problems and novel features will become apparent from the description and accompanying drawings in this specification.

[0011] [Means for Solving the Problem] The method for manufacturing a coated body disclosed in this case includes: (a) applying a first coating liquid to a first surface of a substrate taken out from a transfer section to form a first coating liquid layer; (b) after step (a), applying a second coating liquid onto the first coating liquid layer to form a second coating liquid layer; (c) after step (b), drying the first coating liquid layer and the second coating liquid layer to form a first coating layer and a second coating layer; (d) storing the substrate having the first coating layer and the second coating layer formed thereon in a transfer section. Moreover, step (a) involves applying the first coating liquid to the first surface of the substrate, and step (b) involves spraying the second coating liquid onto the first surface of the substrate.

[0012] The apparatus for manufacturing a coated body disclosed in this case comprises: a transfer section for removing a substrate; a first coating section for applying a first coating liquid to a first surface of the substrate; a second coating section for applying a second coating liquid to the first surface of the substrate; a drying section for forming a coated body on the first surface of the substrate by drying the first coating liquid and the second coating liquid on the substrate; and a transfer section for receiving the substrate on which the coated body is formed. Furthermore, the first coating section applies the first coating liquid to the first surface of the substrate, and the second coating section sprays the second coating liquid onto the first surface of the substrate.

[0013] [Effect of the Invention] According to the method for manufacturing the coating body disclosed in this case, a coating body with good properties can be manufactured.

[0014] According to the coating body manufacturing apparatus disclosed in this case, a coating body with good properties can be manufactured.

Implementation Method

[0016] Hereinafter, embodiments will be described in detail based on examples and drawings. Furthermore, in all the drawings used to describe the embodiments, components with the same function will be labeled with the same element symbols, and repeated descriptions will be omitted.

[0017] (Embodiment 1) FIG1 is a cross-sectional view showing the manufacturing steps of the coating body of this embodiment. FIG2 is a schematic diagram showing the configuration of the manufacturing apparatus for the coating body of this embodiment.

[0018] First, refer to Figure 1 and explain the steps for forming the coating body.

[0019] As shown in Figure 1(A), a substrate 1 made of a porous membrane is prepared. The porous membrane of the substrate 1 may be made of, for example, a polyolefin resin. The thickness of the substrate 1 is, for example, about 5 μm to 50 μm; the width is, for example, about 100 mm to 3000 mm. The pore size distribution of the micropores is, for example, about 10 nm to 10 μm, and the average pore size is, for example, about 10 nm to 900 nm. In addition, the Gurley value of the substrate 1 is, for example, about 100 to 300 sec / 100 cc.

[0020] Next, as shown in FIG1(B), a first coating liquid is applied to the surface of the substrate 1 to form a first coating liquid layer 3a. The first coating liquid has a filler and a dispersion medium. As fillers, inorganic materials such as alumina, silicon dioxide, aluminum hydroxide, and boehmite can be used; cellulose (including cellulose nanofibers), carbon fibers, carbon nanotubes, carbon nanofibers, graphene, fullerenes, and aromatic polyamide fibers can be used. As cellulose, cellulose in which the hydrophilic groups are replaced by hydrophobic groups can be used. As a dispersion medium, an aqueous solvent or an organic solvent can be used. Furthermore, a binder can be added. As a binder, side-chain or cyclic polymer resins, acrylic resins, thermoplastic fluoropolymers, etc. can be used. As a coating apparatus, for example, a gravure coating apparatus can be used. In addition to fillers and binders, it can also be used in a state in which styrene-butadiene rubber (SBR) or a polymer with high ionic conductivity is added.

[0021] Next, as shown in FIG1(C), the second coating liquid is applied to the surface of the substrate 1 to form a second coating liquid layer 4a. The second coating liquid contains water glass and a solvent. The water glass is an aqueous solution of an alkali metal or alkaline earth metal silicate. For example, in addition to sodium silicate (sodium silicate, Na2O‧nSiO2 (n=2~4)), silicates containing Li, K, Rb, Ba, Ca, Mg, Sr, etc. to replace Na (basic silicates) can be used, and one or more can be used alone. As a solvent, an aqueous solvent or an organic solvent can be used. In addition, an adhesive can be added. As an adhesive, a resin (fluororesin) such as polyvinylidene fluoride (PVdF) can be used.

[0022] Next, as shown in FIG1(D), the first coating liquid layer 3a and the second coating liquid layer 4a on the substrate 1 are dried by using a heater 10 or the like, thereby forming a laminated film of coating film 3b and coating film 4b. Through the above steps, a coating body (septum) 5 formed by the substrate (porous membrane) 1 and the coating film 3b and coating film 4b can be formed. The coating film 3b and coating film 4b are breathable, and the Glyph value (breathability, [sec / 100cc]) of the coating body 5 is 10 or more and 3000 or less to ensure breathability.

[0023] The following will describe the case of forming the above-mentioned coating layer using the apparatus (system) shown in FIG2.

[0024] As shown in FIG. 2, the coating body manufacturing apparatus includes: an unwinding section (transfer section) UW for unwinding the substrate 1; and a winding section WD for winding the substrate 1. The substrate 1 is continuously arranged from the unwinding section UW to the winding section WD, and a coating film 3b and a coating film 4b are formed on the surface (first surface) of the substrate 1 between the unwinding section UW and the winding section WD to complete the coating body 5. According to this coating body manufacturing apparatus, the roller-shaped (wind-up strip-shaped) substrate 1 can be continuously processed to effectively form a coating body. In addition, in this specification, the unwinding section UW side is sometimes referred to as the upstream side, and the winding section (transfer section) WD is sometimes referred to as the downstream side.

[0025] Specifically, a first coating treatment section (20), a second coating treatment section (30), and a drying treatment section (40) are disposed between the unwinding section UW and the winding section WD. While the substrate 1 is guided by a plurality of rollers (guide rollers) R, it is processed in each treatment section, and a coating film 3b and a coating film 4b are formed on its surface. Detailed description follows.

[0026] The substrate 1 unwound by the self-unwinding section UW is transported to the first coating processing section (20) by the guide of the roller R. In this first coating processing section (20), a gravure coating device is provided to coat (apply) the first coating liquid 20a on the first surface of the substrate 1 to form the first coating liquid layer 3a.

[0027] The substrate 1 on which the first coating liquid layer 3a is formed is conveyed to the second coating processing unit (30) by the guide of the roller R. In this second coating processing unit (30), a spray coating device is provided to coat (apply) a second coating liquid on the first coating liquid layer 3a on the first surface of the substrate 1 to form a second coating liquid layer 4a.

[0028] The substrate 1, on which the first coating liquid layer 3a and the second coating liquid layer 4a are formed, is conveyed to the drying treatment unit (40). In the drying treatment unit (40), a drying oven (conveyor-type drying oven) 40 is provided, and the liquid components of the first coating liquid layer 3a and the second coating liquid layer 4a of the substrate 1, conveyed by the roller R, are vaporized to form coating films 3b and 4b. For example, the drying oven has a drying chamber (cover), in which heated air is introduced through a nozzle (not shown). The temperature of the heated air is controlled by a heating unit (heater, etc.) (not shown).

[0029] As described above, the strip-shaped substrate 1 is guided by a plurality of rollers (guide rollers) R and is processed in each processing section to form a coated body 5.

[0030] Here, in this embodiment, a gravure coating apparatus for contact coating is used in the first coating processing unit (20), and a spray coating apparatus for non-contact coating is used in the second coating processing unit (30), so that the first coating liquid layer 3a and the second coating liquid layer 4a can be formed with good precision.

[0031] Figure 3 is a cross-sectional view of the gravure coating apparatus. The gravure coating apparatus shown in Figure 3 is a longitudinal coating apparatus, with the chamber (tank) 20b arranged in a vertical direction (parallel to the direction of gravity). This apparatus includes: a chamber (tank) 20b for storing coating liquid 20a; a coating roller (gravure roller) CR, a portion of which is immersed in the chamber (tank) 20b; a first blade 20c for preventing the coating liquid 20a from scattering and adjusting the amount of liquid on the roller surface; and a second blade 20c for preventing leakage of coating liquid in the chamber (tank) 20b and for preventing leakage of coating liquid from the gaps between the coating rollers (gravure rollers). The first blade 20c is configured such that its angle and pressing pressure can be adjusted to adjust the amount of coating liquid 20a adhering to the surface of the coating roller on the rotation direction side of the coating roller CR. Next, the coating liquid 20a adhering to the surface of the coating roller CR is transferred to the surface of the substrate 1 to form a first coating liquid layer 3a. Furthermore, the gravure coating apparatus shown in FIG3 can be either vertical or horizontal. In the case of the horizontal type, the second blade for preventing coating liquid leakage is no longer required, and it is configured to have only a first blade 20c for preventing the coating liquid 20a from scattering and adjusting the amount of liquid on the roller surface.

[0032] Figures 4 and 5 are cross-sectional views of a spray coating apparatus. The spray coating apparatus shown in Figures 4 and 5 is a coating apparatus for a solution that utilizes the electro-spraying phenomenon.

[0033] As shown in Figure 4, the spray coating apparatus sprays the second coating liquid supplied from the liquid supply device LS onto the substrate (first coating liquid layer 3a) 1 via the nozzle N along with a gas. For example, the nozzle N extends along the depth direction of the paper surface, and the nozzle orifice is rectangular in shape with a long side in the depth direction of the paper surface. One or more gases selected from inert gases, oxygen, and air can be used as the gas. The moisture content (humidity) of this gas is preferably 0-90%.

[0034] Here, as shown in FIG. 5, a high voltage HV is applied between the nozzle N and the substrate 1. Alternatively, the high voltage HV can be applied to the roller R in contact with the substrate 1 or between the conveyor belt (not shown) disposed between the substrate 1 and the roller R and the nozzle N. In this way, when a high voltage HV (1kV or more) is applied, a strong electric field is generated at the nozzle tip, and the solution surface at the nozzle tip becomes charged. Thereby, through the interaction between the charged solution surface and the electric field, a conical meniscus called a Taylor cone is formed. Then, when the electric field is further strengthened, the electrostatic repulsion force on the liquid surface is greater than the surface tension, and fine droplets (SP) are ejected from the tip of the Taylor cone. In such fine droplets, the solvent evaporates in a short time and the charge density of the droplets increases. In this way, the droplets are electrostatically split, and the droplets are further miniaturized and adhere to the opposing substrate 1 (electrode) to form a second coating liquid layer 4a. For example, the droplet diameter on the coating surface is 0.01~60μm.

[0035] In this way, by using a spray coating device that utilizes the electro-spraying phenomenon, the second coating liquid layer 4a can be formed uniformly and with excellent controllability.

[0036] Figure 6 is a schematic diagram showing the configuration of the manufacturing apparatus for the coated body of the comparative example. As shown in Figure 6, although a coating apparatus having two gravure coating sections (20A, 20B) can be used to form the first coating liquid layer 3a and the second coating liquid layer 4a, since gravure coating is a contact coating process, when the second coating liquid is coated, the coating roller CR contacts the first coating liquid layer 3a and interferes with the first coating liquid layer 3a. In addition, an undesirable coating liquid mixture layer may also be formed.

[0037] FIG7 is a diagram showing the configuration of the manufacturing apparatus for the coating body of the comparative example. As a coating apparatus capable of performing non-contact coating processing, the coating apparatus using a rotating disk (rotator) 90 shown in FIG7 can be used. However, in this case, it is difficult to control the miniaturization of the plurality of rotating disks and droplets, and it is difficult to form a coating liquid layer with excellent controllability.

[0038] In contrast, in this embodiment, by using a spraying apparatus that utilizes the electro-spraying phenomenon as a coating apparatus for the subsequent stage, the second coating liquid layer 4a can be formed uniformly and with excellent controllability. For example, a thin second coating liquid layer 4a (with a film thickness of about 0.01 to 10 μm) can also be formed.

[0039] Furthermore, in the spray coating apparatus of this embodiment shown in FIG4, it includes: a spray area AS, which sprays ultrafine droplets (mist); an air curtain area A1 located upstream of the spray area AS; and an air curtain area A1 located downstream of the spray area AS. In the air curtain area A1, air is blown along direction a of the spray area AS (nozzle N). In other words, an air nozzle is arranged inclined toward the direction of the spray area AS (nozzle N), and air is blown toward the spray area AS by means of the air nozzle. The angle (θ) between the vertical direction of the substrate 1 and direction a, that is, the angle (θ) between the vertical direction of the substrate 1 and the nozzle, is 0.1° or more and 90° or less. In other words, the angle (θ) between the arrangement direction (vertical direction) of the nozzle N and the inclined direction of the air nozzle is 0.1° or more and 90° or less. As the conveying speed of substrate 1 changes, the flow rates of the accompanying flow into the air curtain region A1 upstream of the spray region AS, the accompanying flow into the spray region AS, and the accompanying flow into the air curtain region A1 downstream of the spray region AS change. Therefore, it is desirable to be able to arbitrarily change the front end position and nozzle angle (θ) of the air nozzle.

[0040] In this way, by providing the air curtain area A1, leakage of mist to the upstream and downstream sides of the spray area AS can be suppressed. In particular, the substrate 1 is transported by providing openings (windows, gaps, substrate inlets, substrate outlets) below the walls separating each area (each chamber A1, AS, A1). Accompanying flow is generated with this transport, that is, wind flowing along the transport direction (travel direction) of the substrate 1. Since the mist leaks along with this accompanying flow, it is particularly preferable to provide the air curtain area A1 on the downstream side of the spray area AS.

[0041] Furthermore, as mentioned above, in the device shown in FIG4, although an air curtain region A1 is provided on both the upstream and downstream sides of the spray region AS, it may also be provided only on the downstream side. Furthermore, in the device shown in FIG5, although the air blowing direction is inclined, it may also be perpendicular to the substrate 1 (θ=90°).

[0042] (Embodiment 2) In this embodiment, an application example of the coating body manufacturing apparatus of Embodiment 1 will be described.

[0043] (Application Example 1) Figures 8 to 10 show cross-sectional views of the spray coating apparatus of this application example. Z represents the accompanying flow, Figure 9 shows the upstream side, and Figure 10 shows the downstream side. In Embodiment 1 (Figure 4), although the air blowing directions of the air curtain area A1 on the upstream and downstream sides of the spray area AS are symmetrical (the angle θ is the same), as shown in Figures 8 to 10, the air blowing angle θb on the downstream side can be made greater than the air blowing angle θa on the upstream side (θb > θa).

[0044] In this way, by increasing the air blowing angle θb on the downstream side, the leakage prevention effect on the downstream side, which is prone to leakage with the accompanying flow Z, can be improved.

[0045] Furthermore, when adjusting the air blowing angle (θa, θb) as described above on the upstream and downstream sides, the air nozzle can be easily tilted by making the length B of the air curtain region A1 on the downstream side greater than the length A of the air curtain region A1 on the upstream side (B>A) in the conveying direction of the substrate 1.

[0046] (Application Example 2) In the downstream air curtain region A1, which is easily affected by the accompanying flow, the air volume of the air nozzles can be increased. The air volume is defined as the amount of air moving per unit time (m3 / min) when using a blower or the like. For example, the air volume of the air nozzles in the downstream air curtain region A1 can be greater than the air volume of the air nozzles in the upstream air curtain region A1.

[0047] (Application Example 3) In the downstream air curtain region A1, which is easily affected by the accompanying flow, the number of air nozzles can be increased. For example, in the downstream air curtain region A1, a plurality of air nozzles can be provided in the depth direction of the paper in FIG4, and their number can be greater than the number of air nozzles provided in the upstream air curtain region A1. In this case, if the air volume of each air nozzle is the same, the air volume of the air nozzles in the downstream air curtain region A1 will become greater than the air volume of the air nozzles in the upstream air curtain region A1.

[0048] Furthermore, the plurality of air nozzles is referred to as an air nozzle group. For example, the plurality of air nozzles in the air nozzle group are arranged in a direction perpendicular to the conveying direction. Also, as the blower for the air nozzle group, one blower (with a fixed airflow for all nozzles) can be used for the plurality of nozzles. Alternatively, a method can be used where one blower is connected to one nozzle. In this case, the airflow of each can be changed, and the outflow of accompanying flow can be further suppressed.

[0049] (Embodiment 3) In this embodiment, an application example of the coating body described in Embodiment 1 will be explained. The coating body formed using the coating body manufacturing apparatus of Embodiment 1 can be used as a separator and is suitable for, for example, lithium-ion batteries.

[0050] Figure 11 is a diagram showing the relationship between the movement of lithium ions (Li+) and charging / discharging. Figure 12 is a cross-sectional perspective view showing the structure of a lithium-ion battery. The lithium-ion battery shown in Figure 12 has a cylindrical can 106, and an electrode assembly is housed in this can 106. The aforementioned electrode assembly is formed by wrapping strips of positive electrode material 101 and negative electrode material 103 around a coating body (separator) 5. The positive electrode current collector on the upper end face of the electrode assembly is joined to the positive electrode cap. The negative electrode current collector on the lower end face of the electrode assembly is joined to the bottom of the can 106. Furthermore, an insulating coating layer (not shown) is provided on the outer peripheral surface of the can 106. In addition, an electrolyte (not shown) is injected into the can 106. Although a cylindrical battery has been described here as an example, the structure of the battery is not limited. For example, a square battery or a stacked battery can be used.

[0051] Thus, the lithium-ion battery has a positive electrode material 101, a negative electrode material 103, a coating (separator) 5, and an electrolyte, with the coating (separator) 5 disposed between the positive electrode material 101 and the negative electrode material 103. The coating (separator) 5 has a large number of micropores. For example, during charging, i.e., when the charger is connected between the positive electrode (positive electrode cap) and the negative electrode (bottom of the can 106), lithium ions inserted into the positive electrode active material are released into the electrolyte. The lithium ions released into the electrolyte move in the electrolyte and reach the negative electrode through the micropores of the separator. The lithium ions that reach this negative electrode are inserted into the negative electrode active material constituting the negative electrode.

[0052] In this way, lithium ions move back and forth between the positive and negative electrode materials (between electrode E1 and electrode E2) through the micropores (not shown) provided in the coating body (separator) 5, thereby enabling repeated charging and discharging (see also Figure 11). In particular, when the coating body (separator) 5 shown in Figure 11 has a thicker film thickness, the resistance of lithium ions passing through the film increases, and the output characteristics of the battery decrease. In addition, since the amount of lithium ion movement is reduced, the amount of electron movement is also reduced, thus reducing the battery capacity. Furthermore, as a coating apparatus for the subsequent stage described in Embodiment 1, etc., by using a spray coating apparatus that utilizes the electro-spraying phenomenon, it is also possible to uniformly and controllably form a very thin film (for example, a film thickness of about 0.01 to 10 μm), and improve battery characteristics (output characteristics, capacity, etc.).

[0053] Next, a method for manufacturing a substrate (porous membrane) coated with a coating liquid will be described. The substrate (porous membrane) can be manufactured, for example, by the following steps.

[0054] Figure 13 is a schematic diagram showing the configuration of a porous membrane manufacturing apparatus (system). For example, a plasticizer (liquid paraffin) and a polyolefin (e.g., polyethylene) are fed into the raw material supply section of the twin-screw compounding extruder (S1) in Figure 13, and the aforementioned plasticizer and polyolefin are compounded in the compounding section. The compounding conditions are, for example, 180°C, 12 minutes, and a shaft speed of 100 rpm.

[0055] The mixture (molten resin) is conveyed from the ejector section to the T-die S2. While the molten resin is extruded from the slit of the T-die S2, it is cooled in the roll cooling device S3 to form a thin film resin molded body.

[0056] Next, the aforementioned film-shaped resin molded body is stretched longitudinally by the first stretching device S4, and stretched laterally by the second stretching device S5.

[0057] Next, the stretched film is immersed in an organic solvent (e.g., dichloromethane) in the extraction tank S6. In the stretched film, the polyolefin (e.g., polyethylene) and the plasticizer (paraffin) are in a phase-separated state. Specifically, the plasticizer (paraffin) forms nano-sized islands. These nano-sized plasticizers (paraffin) are removed by the organic solvent (e.g., dichloromethane) in the extraction tank S6. This allows the formation of a porous membrane.

[0058] Subsequently, the membrane is further stretched laterally by the third stretching device S7 while drying and heat-fixing to alleviate the internal stress during stretching. Next, the porous membrane conveyed by the third stretching device S7 is wound by the winding device S8.

[0059] In this manner, a porous membrane (substrate of embodiment 1) can be manufactured.

[0060] For example, a roll of porous membrane wound by the winding device S8 can be disposed in the unwinding section UW of embodiment 1 (FIG. 2), and a first coating liquid layer 3a and a second coating liquid layer 4a can be sequentially formed on its surface.

[0061] Furthermore, for example, the apparatus of Embodiment 1 (FIG. 2) may also be incorporated between the third stretching device S7 and the winding device S8. That is, the first coating liquid layer 3a and the second coating liquid layer 4a may be sequentially formed on the surface of the porous membrane conveyed by the third stretching device S7. In this case, the winding device S8 corresponds to the winding section WD in FIG. 2.

[0062] In this way, the coating body can be formed by a continuous device (system) from the formation of the porous membrane to the formation of the coating layer.

[0063] (Embodiment 4) Figure 14 shows the precipitation state of cellulose (Theoras) in Embodiment 4. Equal amounts of cellulose monomer (untreated cellulose) and a chemically modified agent (semi-esterified (SA)) for the hydrophobic groups on the cellulose surface were added to water and allowed to stand for 24 hours (Figure 14). The amount added was 10 g. SA esterification refers to the removal of unreacted additives after esterification of cellulose using an additive (succinic anhydride).

[0064] As shown in Figure 14, SA-modified cellulose exhibits less sedimentation after standing for 24 hours compared to untreated cellulose. This is due to the electrostatic repulsion effect generated by the hydrophobic groups on the surface of the modified cellulose molecules. Therefore, by adding this hemiesterified cellulose to the liquid sprayed in the spray area AS, the electrostatic repulsion on the liquid surface is further increased, enabling finer droplets to be sprayed from the tip of the Taylor cone.

[0065] In this way, by chemically modifying the surface of fillers such as cellulose, the electrostatic repulsion of the filler can be improved, and finer droplets can be coated.

[0066] (Embodiment 5) Figures 15 and 16 show the precipitation state of cellulose in Embodiment 5. Equal amounts of a chemically modified (semi-esterified (SA)) agent on the surface of cellulose and a secondary chemically modified (SAPO) agent using propylene oxide to modify the hydrophobic groups of SA-modified cellulose were added to water. The state immediately after addition is shown in Figure 15. The state after standing for 24 hours is shown in Figure 16. As shown in Figure 16, when comparing the precipitation states of SA-modified cellulose and SAPO-modified cellulose after standing for 24 hours, it was confirmed that SAPO-modification was more effective in suppressing precipitation than SA-modification. This is because the increased number of modified hydrophobic groups on the surface of the cellulose molecules further enhances the electrostatic repulsion compared to SA-modification. Therefore, not only SA-modification as described in Embodiment 4, but also the addition of SAPO-modified cellulose to the liquid sprayed in the spray area AS significantly enhances the electrostatic repulsion on the liquid surface, enabling the ejection of fine droplets from the tip of the Taylor cone.

[0067] In this way, by chemically modifying the surface of fillers such as cellulose, the electrostatic repulsion of the filler can be improved, and finer droplets can be coated.

[0068] The invention made by the inventor of this case has been specifically described above based on the embodiments and examples. However, the present invention is not limited to the above embodiments or examples. Obviously, various changes can be made without departing from its spirit.

[0069] For example, in Embodiment 1, although a diaphragm having a coating layer (coating film 3b and coating film 4b) on a substrate made of a porous film is used as an example to illustrate the process, the coating technology described in Embodiment 1 can also be applied to an electrode having a coating layer on a metal foil that serves as a substrate.

[0070] For example, in the first coating solution, graphite and nano-Si, which are the negative electrode active materials, are added to a mixture 1 formed by mixing an organic solvent with hydrophobic cellulose nanofibers (CeNF) dispersed in water; and a mixture 2 containing CNTs (carbon nanotubes) or acetylene black can also be used as the conductive material. Besides nano-silicon (Si), widely used and common materials such as graphite, hard carbon (difficult-to-graphitize carbon), soft carbon (easily graphitized carbon), and lithium titanate (Li4Ti5O12) can also be used as the negative electrode active material. Furthermore, Ketjen black, carbon nanofibers, etc., can be used as other conductive materials besides CNTs and acetylene black. Regarding the second coating solution, the above-mentioned coating solution can also be used, and as described above, a first coating layer 3a and a second coating layer 4a are formed on a metal foil, and dried by a heater 10, etc., to form a laminated film (negative electrode) of coating film 3b and coating film 4b.

[0071] Furthermore, in the first coating liquid, the mixture 3, which is a mixture of an organic solvent and hydrophobic cellulose nanofibers (CeNF) dispersed in water, can suspend positive electrode active materials such as NCM, NCA, LiNiO2, Li2MnO3-LiMO2, and Li2MSiO4, as well as conductive materials and binders such as PVDF, and the resulting slurry of the mixed materials can be used. As for the second coating liquid, the above-mentioned coating liquid can also be used, and as described above, a first coating liquid layer 3a and a second coating liquid layer 4a are formed on a metal foil, and dried by a heater 10 or the like, to form a laminated film (positive electrode) of coating film 3b and coating film 4b.

[0072] In this way, the first coating liquid containing the electrode active material and the aforementioned second coating liquid can be sequentially coated on the metal foil as described in the aforementioned embodiment.

[0073] Furthermore, the coating layer on the substrate can be two or more layers. That is, when a coating layer as a lower layer has already been formed on the substrate, and a coating layer as an upper layer is to be formed, the effects described in Embodiment 1 can be produced by spraying, i.e., performing the non-contact coating process described in Embodiment 1. For example, a coating film can be further formed on the coating film 3b and the coating film 4b by spraying as a non-contact coating process.

[0074] Furthermore, regarding the method for forming the lower coating layer (e.g., coating film 3b), in addition to gravure coating as a contact coating process, coating with a bar coater can also be used. Alternatively, coating with a die coater can also be used. Thus, the method for forming the lower coating layer (e.g., coating film 3b) can be either contact coating or non-contact coating. For example, a three-layer coating film can be formed using contact coating → non-contact coating → non-contact coating. Furthermore, a three-layer coating film can also be formed using non-contact coating → non-contact coating → non-contact coating. [Simplified Explanation of the Diagram]

[0015] [Fig. 1] is a cross-sectional view showing the manufacturing steps of the coated body in Embodiment 1. [Fig. 2] is a schematic diagram showing the structure of the manufacturing apparatus for the coated body in Embodiment 1. [Fig. 3] is a cross-sectional view showing the gravure coating apparatus. [Fig. 4] is a cross-sectional view showing the spray coating apparatus. [Fig. 5] is a cross-sectional view showing the spray coating apparatus. [Fig. 6] is a schematic diagram showing the structure of the manufacturing apparatus for the coated body in the comparative example. [Fig. 7] is a diagram showing the structure of the manufacturing apparatus for the coated body in the comparative example. [Fig. 8] is a cross-sectional view showing the spray coating apparatus for Application Example 1. [Fig. 9] is a cross-sectional view showing the spray coating apparatus for Application Example 1. [Fig. 10] is a cross-sectional view showing the spray coating apparatus for Application Example 1. [Fig. 11] is a diagram showing the relationship between the movement of lithium ions (Li+) and charging / discharging. [Fig. 12] is a cross-sectional perspective view showing the structure of a lithium-ion battery. [Figure 13] is a schematic diagram showing the configuration of the apparatus (system) for manufacturing a porous membrane. [Figure 14] is a diagram showing the precipitation state of cellulose (Theoras) in Embodiment 4. [Figure 15] is a diagram showing the precipitation state of cellulose in Embodiment 5. [Figure 16] is a diagram showing the precipitation state of cellulose in Embodiment 5.

Claims

1. A method for manufacturing a coated body, comprising: (a) applying a first coating liquid to a first surface of a substrate taken from a loading section to form a first coating liquid layer; (b) after step (a), applying a second coating liquid onto the first coating liquid layer to form a second coating liquid layer; (c) after step (b), drying the first coating liquid layer and the second coating liquid layer to form a first coating layer and a second coating layer; and (d) storing the substrate having the first coating layer and the second coating layer formed thereon in a loading section; wherein step (a) involves applying the first coating liquid to the first surface of the substrate; and step (b) involves spraying the second coating liquid onto the first surface of the substrate; wherein the first coating liquid has a first filler and a second filler; and wherein the first filler is selected from materials such as alumina, silicon dioxide, aluminum hydroxide, and boehmite. The aforementioned second filler is selected from materials such as cellulose, carbon nanofibers, carbon nanotubes, cellulose nanofibers, graphene, and fullerene.

2. A method for manufacturing a coated body, comprising: (a) applying a first coating liquid to a first surface of a substrate taken from a loading section to form a first coating liquid layer; (b) after step (a), applying a second coating liquid onto the first coating liquid layer to form a second coating liquid layer; (c) after step (b), drying the first coating liquid layer and the second coating liquid layer to form a first coating layer and a second coating layer; and (d) storing the substrate having the first coating layer and the second coating layer formed thereon in a loading section; wherein step (a) involves applying the first coating liquid to the first surface of the substrate; and step (b) involves spraying the second coating liquid onto the first surface of the substrate; the first coating liquid has a first filler and a second filler; and the first filler is selected from materials such as alumina, silicon dioxide, aluminum hydroxide, and boehmite. The aforementioned second filler is selected from materials such as cellulose, carbon nanofibers, carbon nanotubes, cellulose nanofibers, graphene, and fullerene; the aforementioned second coating liquid is an alkaline silicate.

3. An apparatus for manufacturing a coating body, comprising: a transfer section for removing a substrate; a first coating section for applying a first coating liquid to a first surface of the substrate; a second coating section for applying a second coating liquid to the first surface of the substrate; a drying section for forming a coating body on the first surface of the substrate by drying the first coating liquid and the second coating liquid on the substrate; and a transfer section for receiving the substrate on which the coating body is formed; wherein the first coating section applies the first coating liquid to the first surface of the substrate; the second coating section sprays the second coating liquid onto the first surface of the substrate; the first coating liquid has a first filler and a second filler; the first filler is selected from materials such as alumina, silicon dioxide, aluminum hydroxide, and boehmite; and the second filler is selected from materials such as cellulose, carbon nanofibers, carbon nanotubes, cellulose nanofibers, graphene, and fullerene.

4. An apparatus for manufacturing a coated body, comprising: a transfer section for removing a substrate; a first coating section for applying a first coating liquid to a first surface of the substrate; a second coating section for applying a second coating liquid to the first surface of the substrate; a drying section for forming a coated body on the first surface of the substrate by drying the first coating liquid and the second coating liquid on the substrate; and a transfer section for receiving the substrate on which the coated body is formed; wherein the first coating section applies the first coating liquid to the first surface of the substrate; the second coating section sprays the second coating liquid onto the first surface of the substrate; the first coating liquid has a first filler and a second filler; the first filler is selected from alumina, silica, aluminum hydroxide, and boehmite; the second filler is selected from cellulose, carbon nanofibers, carbon nanotubes, cellulose nanofibers, graphene, and fullerene; and the second coating liquid has an alkaline silicate.

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